Projecting video directly onto the retina

With the head-mountable, augmented reality Google Glass capturing tons of attention in the press, it was only a matter of time before we saw a DIY retina projector. This isn’t a new build; [Nirav] has been working on it for a few months, but it might just be time for this information to be useful to someone.

A retina projector focuses laser light though beam splitters and concave mirrors to create a raster display on the back of your eye. There’s an incredible amount of research into this field, but not many DIY projects. To make this project a reality, [Nirav] picked up a SHOWWX laser video projector and mounted it in a 3D printed frame along with a few pieces of optical equipment.

[Nirav]‘s build isn’t without its drawbacks, though. The exit pupil, or the apparent size of the image, is only about 1.5 mm wide and much too small to be of any real use. Also, commercial retina projectors have an output of a puny 2 microwatts, where [Nirav]‘s laser projector puts out 200 millwatts. This is more than enough to permanently damage your eye.

29 thoughts on “Projecting video directly onto the retina

  1. If the Googles have a virtual retina display (vrd), which looks possible given this build, optics would be bright no matter the ambient light. And with proper use of mirrors could be adjusted to appear in focus and across a large area of the users field of view.

    This is an awesome, and pretty ballsy, step towards a inexpensive hacked HMDs.

    Makes me wonder if anyone carries those ultra low power eye-safe laser diodes…

  2. Another key point will be hacking the Google Glasses when they’re out. I mean we’re not likely going to build superior hardware, but I don’t want to run around all day with a Google spycam on my nose.

    To the point with the laser:
    Couldn’t you just PWM it really fast?
    The retina is water-cooled, so the pulse output does not matter as much as the overall power that is brought onto it.
    Or do lasers not work like this?
    I guess there’s a minimum power that has to be used in order to get any light out of it.

    1. Yes, fast PWM would be eye-safe as long as it continues to work properly.

      But think worst-case scenario. What if the PWM is under MCU control (likely in a miniaturized DIY device) and ESD causes the MCU to glitch, erroneously setting duty cycle to 100%? Even if you provide direct protection at vulnerable points, ESD can be very tricky; even a shunted ESD event can still be coupled to unexpected circuits either capacitively or inductively.

      Better to start with a low-power laser, limiting power further if needed with more foolproof resistors/optics.

      1. Same protection as with any power converter, you add a capacitor to only pass AC, diode to offset it from the ground and a pulldown resistor to sink the residue charge from the MOSFET gate when it stops pumping.

      1. From the looks of it I think it’s meant to hook to an android device, not be one, which is even better. If that’s the case it’s likely connected through bluetooth.

  3. The book “Ready Player One” references this type technology for the OASIS game system. I’m really excited to see how this progresses. Also, if you haven’t read the book, do so. It’s 80′s nostalgia meets eXitenZ meets World of Warcraft.

  4. I did a university research paper about this maybe 5 years ago. At that point there was only one company with a working retina projection system and that was Microvision. They’re still around, and they mainly do military equipment for heli pilot HUDs (think of the flip down displays you sometimes see on pilot helmets). Can’t wait to see this tech move to the general public. It was an issue then to get green a blue lasers, but now that those are more readily available you just need to find lasers weak enough (yeah, good luck finding a microwatt green or blue laser outside of a lab) to install into this system. In order for this kind of a system to be safe the absolute maximum output of the laser (as determined by hardware) has to be far less than what it would take to damage your eye. This would take care of a worst case scenario of the beam (or three) being forced on full blast and not moving. At this point I haven’t seen a 3 color system that’s been able to do this.

    1. There are non DPSS blue (445 nm) laser diodes now. I’m not sure about low power as they are used in projectors and are around 1W, but my (relatively uneducated) guess is that since it’s a direct output, they could make lower powered ones rather easily (like they could / can? with red and bluray).

      Green on the other hand, good luck.

    2. Funny you should mention Microvision, the laser projecter used in the project above is a Microvision ShowWX. I got one of those earlier this year and it’s a very nice little gadget, but I wouldn’t dare stare into it without a significantly strong filter.

  5. It would be easy enough to drop the output power using a wideband Nd filter. I’m sure it wouldn’t be hard to find a 1×10^3 filter.

  6. Yay..microwaves and retinas beaming.. your health is screwed but at least you have cool gadgets that have no automation/productivity value..

  7. Doubleplus Karma upon this Hack’s creator for opening up their work. We’ve only reached some stages of development from such caring enough to share!

    But- design of things that can screw up your life demands respect.

    Here’s where *I* care enough to share a few “Thought Hacks” to prevent you from needing text-to-speech software. Think about that last one a moment, eh? Laser and Eye are two concepts to keep safely apart. Or- you are literally “Betting Eyes” on getting our tech to be safe.

    Yes, I coldly intended that the initial amusement at a safetynanny oldster’s appearing to tease folks would get slapped by a more grim reality check.

    Think on how deeply and truly it would suck to become blind. I cannot be too unsubtle about this.

    True or false query folks:

    Artificial eyes are cheap and easily obtained.

    Answer is TRUE and they’re sadly not going to let you see anything- as they are just a glass or plexi ball.

    Even a sheet of paper can cut.

    If you doubt the wisdom of what I’ve said. I hope you’re good with text-to speech and IVR tech.

  8. Honestly, I don’t see how they could work, considering just how narrow (7 degrees? Less?) that angle of full clarity is. (Don’t believe me? Look at a wall of text, then, while keeping your eyes focused on one particular word, see how many words out left/right/up/down from there you can read. Shocking, isn’t it?) By the time you get out to 45 degrees from center, pixels would have to grow to an inch across (at two feet) to even be discernible.

    (It goes without saying that if someone can point out a credible source, I have no problem retracting my statement.)

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